Exciton Dynamics

Abstract

One major consequence of the Coulomb interaction between electrons and holes in semiconductors is the formation of excitons with a hydrogenic series of bound states converging to the bandgap energy. It is now well-known that excitons profoundly influence optical properties of a large number of insulators, molecular crystals and semiconductors. Theory of excitons was first developed by Frenkel [6.1], Peierls [6.2], and Wannier [6.3] in 1930s in an attempt to understand the basic absorption mechanism in solids. Excitons are classified into two types: Frenkel excitons for which the electron-hole pair is very tightly bound, and Wannier excitons where the electron orbits around a hole with a large radius. Excitons in semiconductors are generally Wannier excitons with large radii [6.4].